A conventional coded picture data reproducing apparatus will be explained in reference to FIGS. 16 to 21.
FIG. 16 is a block diagram showing a conventional coded picture data reproducing apparatus.
The coded picture data reproducing apparatus, as shown in FIG. 16, is comprised of a microprocessor Mp, a key input system Kb, a motor drive circuit Mdd, a disc drive motor Dm, a motor drive circuit Mdp, an optical pickup drive motor Pm, an optical pickup Pu, a syntax decoder Sx, an MPEG decoder Mpg, a frame buffer Fb, a video D/A (Digital to Analog) converter Vda and a front-end processor Fep.
The front-end processor Fep is comprised of a data detecting circuit Ds and an error correction code (hereinafter referred to ECC) processing circuit Ec.
A turntable (not shown) for loading thereon the optical disc D is coupled to a rotor shaft of the disc drive motor Dm. The turntable is driven by the rotation of the rotor shaft and thus rotates the optical disc D loaded thereon.
The video D/A converter Vda has an analog video signal output terminal which is capable of mechanically and electrically connecting to a signal line.
The signal line is able to be both mechanically and electrically connected to a video input terminal of the monitor Mnt having a display device such as a liquid crystal device or a cathode-ray tube. The video D/A converter Vda forwards video signals to the monitor Mnt via the signal line.
The monitor Mnt displays a picture image on its display screen according to the input video signal.
Further, the MPEG decoder Mpg has an output terminal which is capable of outputting a digital video signal.
The microprocessor Mp is connected to the key input system Kb, the motor drive circuit Mdd and the motor drive circuit Mdp via the signal line.
The microprocessor Mp is connected to the front-end processor Fep, the syntax decoder Sx and the MPEG decoder Mpg via the two-way bus line.
Further, the microprocessor Mp controls circuit blocks connected thereto according to the command provided through a key-input system Kb.
For instance, when the user command for directing a reproduction of the picture data recorded on the optical disc D is forwarded from the key input system Kb to the microprocessor Mp, the microprocessor Mp forwards operation signals to the motor drive circuit Mdd and the motor drive circuit Mdp for making them rotate the optical disc D.
The motor drive circuits Mdd and Mdp receive the operation signals from the microprocessor Mp and then forward driving signals to a disc drive motor Dm and an optical pickup drive motor Pm respectively coupled thereto.
The disc drive motor Dm rotates the optical disc D at the rotation speed according to the driving signal.
The optical pickup drive motor Pm moves the optical pickup Pu to the optical disc D in the radius direction according to the driving signal so that the optical pickup Pu search the picture data to be reproduced.
The optical pickup Pu irradiates a laser beam to the signal recording surface of the optical disc D so as to obtain record signal based on the reflection light.
The disc is recorded thereon picture data and addresses for indicating the record positions of the picture data. And the optical pickup Pu is moved according to the address to search the picture data to be reproduced.
The optical pickup Pu searches the picture data to be reproduced, and then obtains the record signal corresponding to the picture data on the disc.
The record signal picked up by the optical pickup Pu is forwarded to the data extracting circuit Ds which is contained in the front-end processor Fep, which is located in rear of the optical pickup Pu.
The record signal is a wave-formed signal called a RF signal. The data extracting circuit Ds slices the RF signal at a specific timing so as to generate a rectangular wave-formed data signal.
Further, the data extracting circuit Ds forwards the data signal to the ECC processing circuit Ec on the rear.
The data signal is record by executed a NRZI (Non Return to Zero Inverted) modulation at recording time.
The ECC processing circuit Ec extracts a data signal from the invert interval of the data signal according to the NRZI demodulation rule, and performs the error correction of the data in each ECC block, then it forwards the data signal to the syntax decoder Sx located in rear of the circuit Ec.
The syntax decoder Sx extracts the control data from the input data signal according to the command that is output from the microprocessor Mp. Further the syntax decoder Sx extracts the picture data and forwards the picture data to the MPEG decoder Mpg located in rear of the decoder Sx.
The picture data is coded in the MPEG (Moving Picture Expert Group) system. The picture data is decoded in the MPEG decoder Mpg by the command output from the microprocessor Mp according to the decoding algorithm of pre-determined MPEG system.
A frame buffer Fb, which is connected to the MPEG decoder Mpg via the two-way bus line works as a work memory for temporarily storing the picture data when the MPEG coded picture data is decoded.
The picture data temporarily stored in the frame buffer Fb is added a synchronizing data for every frame, then it is output to the video D/A converter Vda located in rear of the MPEG decoder Mpg.
Or the MPEG decoder Mpg could output the picture data from the digital video signal output terminal as the digital video signal.
The video D/A converter Vda converts the input picture data into the analog video signal.
Then, the video D/A converter Vda forwards the video signal which is converted to the analog signal to the monitor Mnt located in rear of the converter Vda, via the signal line.
The monitor Mnt displays the picture image on a display device such as a liquid crystal device or a cathode-ray tube according to the input video signal.
In the coded picture data reproducing apparatus according to the present invention, the picture image is reproduced in the way as mentioned above.
Here, the decoding algorithm of the MPEG decoder Mpg will be explained in reference to FIG. 17.
FIG. 17 illustrates a data structure of the picture data of the MPEG system.
The MPEG system is one of the predictive coding schemes based on the correlation between picture frames. The coded picture data is comprised of a plurality of groups of pictures (hereinafter referred to GOP).
One GOP is comprised of a plurality of frames. Each frame is a coded picture data comprised of a picture data of an intraframe coded picture (I-picture), a plurality of interframe forward predictive coded pictures (P-pictures) and a plurality of bi-directional predictive coded pictures (B-pictures).
In FIG. 17, the frames of the I-picture, P-picture and B-picture in the (N−1)-th through (N+R)-th GOPs are arranged in the sequence of reproducing for convenience of explanation.
Specifically, the sequence of reproducing the frames of the pictures will be in the sequence of B→B→I→B→B→P→B→B→P→B→B→P.
When the MPEG coded data are actually transmitted or recorded, the data are transmitted or recorded in the sequence different from the above-mentioned sequence.
Specifically, the sequence for transmitting or recording the pictures will be in the sequence of I→B→B→P→B→B→P→B→B→P→B→B.
The above-mentioned pictures are coded in a predetermined sequence according to the correlation between picture frames
Each of the above-mentioned pictures is an example illustrating a part of the GOP. While the number of pictures is not limited to the above examples.
For instance, although two B-pictures precede the I-picture in their reproducing sequence, the number of B-pictures preceding the I-picture may be three.
As described above, the MPEG system is a coding system of the picture signal according to the predictive coding scheme.
Especially, since the MPEG system is subjected to moving pictures, the data of each frame can be coded based on the correlation between the I-picture data which will be a frame standard of the moving picture and the P-picture data, B-picture data which are coded the difference of the I-picture data.
Specifically, an amount of change between frames of the moving picture before coding the frames is transformed to a motion-adaptive vector. Then the pictures of the frames are coded so as that they are predictively interpolated based on the motion-adaptive vector.
As a sequence of coding the data, initially the picture signal of the fame to be made as an I-picture is coded. Secondarily the picture signal of the frame to be made as a P-picture based on its correlation to the coded I-picture is coded. And thirdly, the picture signal of the frame to be reproduced between the I-picture and the P-picture is coded as a B-picture based on its correlations to both the I-picture and the B-picture.
Further, as the sequence of coding the pictures are predetermined, the sequence of decoding the pictures are also predetermined.
That is, initially, the picture data of the I-picture is decoded. Secondarily, the picture data of the P-picture is decoded by using the picture data of the decoded I-picture. And thirdly, the picture data of the B-pictures are decoded by using the picture data of the decoded I-picture and the P-picture.
A reason for that the sequences of the coding and the decoding are predetermined is that the P-picture and B-pictures are coded in reference to the I-picture.
Especially, since the B-pictures are coded with reference to the I-picture and P-pictures, the B-picture have to be decoded by using the already decoded I-picture and B-pictures.
As shown in FIG. 17, when the B-picture data B1, B2 belonging to the N-th GOP are decoded, first the P-picture data Pp which is reproduced last in the (N−1)-th GOP reproduced just before the B-picture data is decoded, then the I-picture data Ip belonging to the N-th GOP is decoded, after that the B-picture data B1, B2 are decoded by using the decoded P-pictures and the I-pictures.
The MPEG decoder Mpg, as shown in FIG. 16, temporarily stores the picture data for two GOPs in the frame buffer Fb and decodes the I-picture data Ip, the P-picture data Pp and the B-picture data B1, B2 in the sequence as mentioned above. Accordingly, in a normal reproduction the P-picture data Pp belonging to the (N−1)-th GOP, the B-picture data B1, B2 and I-picture data Ip belonging to the N-th GOP are continuously decoded, then the picture data is temporarily stored in the frame buffer.
That is, the picture data corresponding to all of the frames in the N-th GOP and the (N−1)-th GOP reproduced just before the N-th GOP are temporarily stored in the frame buffer Fb.
As shown in FIG. 17, even in the case that the P-picture data reproduced last in the (N−1)-th GOP that is reproduced just before the N-th GOP is used for decoding the B-picture data B1, B2 corresponding the frame reproduced in preceding the I-picture data Ip in the N-th GOP, the P picture data Pp which is temporarily stored in the frame memory Fb could be quoted, so that all of the frames are able to be decoded consecutively.
Now a repetitive reproduction in the conventional coded picture data reproducing apparatus will be explained hereinafter.
Here, the start-frame and the end-frame for the repetitive reproduction are each marked as the position A and the position B in FIG. 17.
After the A and the position Bs are designated as a start-frame and a end-frame, respectively, the picture between these two positions is repetitively reproduced, first the optical pickup Pu decodes the P-picture data on the position B which belongs to the (N+R)-th GOP and searches the picture data on the position A which belongs the N-th GOP, thus it obtains the picture data of all of the fames belonging to the GOP as mentioned above.
Then, the MPEG decoder Mpg decodes the fetched picture data.
However, if the N-th GOP is not the closed type GOP, as mentioned above the decoded P-picture data Pp corresponding to the P-picture frame which will be reproduced last in the (N−1)-th GOP is essential for decoding the B-picture data B1, B2 which correspond to the P-picture frame in the (N−1)-th GOP and the I-picture frame in the N-th GOP. That is, the B-picture data B1, B2 are not decoded by only the picture of the frame belonging to the N-th GOP.
Here, the operation of the coded picture data reproducing apparatus, as shown in FIG. 16, will be explained in reference to the flowcharts, as shown in FIGS. 18 through 21.
FIG. 18 illustrates a main routine in the operation of the conventional coded picture data reproducing apparatus.
FIG. 19 illustrates a first sub-routine in the operation of the conventional coded picture data reproducing apparatus.
FIG. 20 illustrates a second sub-routine in the operation of the conventional coded picture data reproducing apparatus.
These main routines and the first and the second sub-routines mentioned above are connected by the nodes 1 to 3.
The programs shown by the flowcharts have been installed in the microprocessor Mp, as shown in a block diagram of FIG. 16. That is, the microprocessor Mp controls the optical pickup Pu or the MPEG decoder Mpg in the coded picture data reproducing apparatus by the command according to the determination and/or processing steps, as shown in the flowchart, so as to execute the repetitive reproduction of pictures between the start-frame and the end-frame that are designated by the key input system Kb.
In FIG. 18, S61 denotes the “START” step of this program.
Following the “START” step S61, the process goes to step S62.
In step S62, an initial value is substituted for the arguments N and R to search the MPEG encoded picture data in every GOP which are recorded on the optical disc D.
The values N and R are stored in the internal memory of the microprocessor Mp.
In step S62, the value N is set to the positive integer larger than 0, and the value R is set to −1.
Next, the process goes to step S63.
In step S63, the optical pickup Pu is driven by the optical pickup drive motor Pm in order to search and obtain the picture data belonging to the (N+R)-th GOP.
Then, the picture data is decoded per each frame of the GOP in the MPEG decoder Mpg. After that all of the decoded picture data are temporarily stored in the frame buffer Fb.
To start the reproduction of the picture data, the picture data of the frames of the pictures are forwarded to the video D/A converter Vda on the rear in the reproducing sequence.
The video D/A converter Vda starts the conversion of the input picture data into the analog video signal, and then sequentially forwards the converted video signal to the monitor Mnt via the signal line.
The monitor Mnt starts the reproduction of the picture by the input video signal.
Since the value N is set to the positive integer larger than 0, and the value R is set to −1 in the previous step S62, the picture data fetched first will be the data belonging to the (N−1)-th GOP.
Next, the process goes to step S64.
In step S64, at the reproducing time of the picture data belonging to the (N+R)-th GOP it is discriminated whether or not the start-frame (position A) is designated.
The start-frame (position A) that is the start position for the repetitive reproduction is designated by pressing a start position designation key mounted through a key-input system Kb.
In case that the determination in step S64 results in “YES”, i.e., when it is determined that there is a designation of the start-frame (position A), the process goes to the first sub-routine, as shown in FIG. 19, via the node 1.
However, in case that the determination in step S64 results in “NO”, i.e., when it is determined that there is no designation of the start-frame (position A), the process goes to step S65.
In step S65, the argument R is incremented by 1 in order to search and obtain the picture data belonging to the next GOP.
Since the initial value R is set to the value −1 in step S62, the picture data fetched next will be belonged in the N-th GOP.
As described above, the value R is stored in the internal memory of the microprocessor Mp. The microprocessor Mp obtains the picture data belonging to the GOP based on the argument R by the optical pickup Pu.
Next, the process goes to step S66.
In step S66, it is discriminated whether or not the reproducing operation of the coded picture data reproducing apparatus is completed.
The judgment if the reproducing operation is completed or not is determined whether or not an end key mounted through a key-input system Kb has been pressed.
If it is determined that a designation for an end-frame (position B) has been made, and then determined that the reproduction has completed, i.e., the determination has resulted in “YES” in step S66, the process goes to the “END” step S67 and become complete.
However, in case that the determination results in “NO”, i.e., when it is not determined that the STOP-key has been pressed, and that the reproducing is not complete, the process of step S63 is again executed.
Here, the processing's from step S63 to step S66 are repetitively executed till it is discriminated that the reproducing processing is completed in step S66, thus the picture data belonging to GOP is sequentially fetched and the fetched picture data is sequentially reproduced per each frame.
Steps from S63 to S66 form a conditional loop for reproducing the picture data belonging to GOP per each frame successively.
In this consecutive reproduction, the optical pickup Pu which is controlled by the microprocessor Mp obtains the data as tracing the data truck formed on the truck of disc D.
The picture data belonging to each GOP is sequentially recorded on the data truck. Thus, if the optical pickup Pu traces the data truck, the coded picture data reproducing apparatus obtains the picture data belonging to each GOP sequentially inevitably so as to carry out the successive reproducing.
Next, the first sub-routine of this program will be explained in reference to FIG. 19.
The first sub-routine performs the main routine, as shown in FIG. 18, and the program of the node 1 and following programs.
The process of step S68 is carried out when the determination in step S64 results in “YES”, i.e., when it is determined that there is a designation of the start-frame (position A).
In this time, the microprocessor Mp makes the number of the designated start-frame be stored in its internal memory.
The frame number is a relative information showing the position of the frame in the GOP.
The process goes to step S69.
In step S69, the microprocessor Mp makes the number of the GOP containing the picture data of the start-frame be stored in its internal memory.
In the program, the number of the GOP containing the start-frame is defined as X.
Then, by substituting the value N+R for the value X, the number of the GOP containing the start-frame is stored in an internal memory of the microprocessor Mp.
In this time, an address which is used for searching the picture data belonging to the GOP is also stored in the internal memory by linked to the GOP number, so that the address is quoted based on the GOP number.
The microprocessor Mp is able to search the picture data of the designated start-frame based on the GOP number and the start-frame number that are stored in the internal memory.
Next, it goes to the judgment processing in step S70.
In step S70, it is discriminated whether or not the (N+R)-th GOP wherein the picture data of the designated start-frame is contained is a closed type.
Whether the GOP is closed type or not is determined by the value of the GOP type flag that is the control data applied to each GOP is one or zero.
The GOP type flag is contained in the control data that is extracted by the syntax decoder Sx. The syntax decoder Sx extracts the control data for each GOP.
An entire picture data belonging to the closed type GOP is able to be decoded without the use of the picture data of the frame belonging to other GOP.
As mentioned above, the picture data belonging to the non-closed type GOP are not able to be decoded unless using already decoded P-picture data corresponding to last frame that is reproduced last in the GOP to be reproduced just before the GOP containing the B-picture corresponding to the frame which is reproduced in preceding the frame corresponding to the I-picture.
Here, if the result of determination of the GOP type is YES, that is, if the microprocessor Mp determines the GOP type a closed type GOP based on the GOP type flag, the process goes to step S71.
If the result if NO, that is, if the GOP is not a closed type, the process goes to step S72.
In step S71, the microprocessor Mp sets the GOP type flag to “1”.
In step S72, the microprocessor Mp sets the GOP type flag to “0”.
When completed the processes in both steps S71 and S72, the microprocessor Mp carries out the determination process in step S73.
In step S73, it is discriminated whether or not the end-frame (position B) is designated at reproducing time of picture data belonging to the (N+R)-th GOP.
The end-frame (position B) is designated by pressing an end position designation key mounted through a key-input system Kb.
In case that the determination in step S74 results in “YES”, i.e., when it is determined that there is a designation of the end-frame (position B), the process goes to the second sub-routine, as shown in FIG. 6, via the node 2.
However, in case that the determination in step S73 results in “NO”, i.e., when it is determined that there is no designation of the end-frame (position B), the process goes to step S74.
In step S74, an argument R is incremented by 1 in order to search and obtain the picture data belonging to the next GOP.
Next, the process goes to step S75.
In step S75, the microprocessor Mp drives the optical pickup Pu by the optical pickup drive motor Pm so as to search and obtain the picture data belonging to the (N+R)-th GOP.
Here, since the value R is incremented by “1”, the fetched picture data belongs to another GOP that follows the GOP wherein the start-frame belongs.
Then, the picture data in the GOP is decoded in every frame by the MPEG decoder Mpg. All of the decoded frame data are temporarily stored in the frame buffer Fb.
To start the reproduction of the picture data, the frames of the pictures are forwarded to the video D/A converter Vda on the rear in the reproducing sequence.
Then, the video D/A converter Vda starts the conversion of the input picture into the analog video signal, and then it sequentially displays the converted video signal as a picture on the monitor Mnt via the signal line.
Accordingly, the monitor Mnt displays the pictures of the fetched GOPs based on the input video signals.
That is, a series of the processes across steps S70 to S75 is repetitively executed and thus the picture data belonging to GOP on the data truck are sequentially reproduced, unless the end-fame is designated through the key input system Kb and the microcomputer Mp determines in step S73 to that an end-frame has been designated.
Steps from S70 to S75 form a conditional loop for consecutively reproducing the GOPs.
As mentioned above, at the successive reproducing time of GOP, the optical pickup Pu which is controlled by the microprocessor Mp obtains the picture data as tracing the data truck formed on the truck of disc D.
Next, the second sub-routine of this program will be explained in reference to FIG. 20.
The second sub-routine is programmed to execute the process following the first sub-routine, as shown in FIG. 20, via the node 2. That is, the second sub-routine is a program for the repetitive reproduction to be executed when designated the end-frame (position B).
The process of step S76 is carried out when the determination in step S73 results in “YES”, i.e., when it is determined that there is a designation of the end-frame (position B).
In this time, the microprocessor Mp makes the number of the designated start-frame be stored in its internal memory.
The frame number is a relative information showing the position of the frame in the GOP.
The microprocessor Mp carries out the process of step S77 after the process of step S76 has completed.
In step S77, the microprocessor Mp substitutes the value X, i.e., the number of the GOP to which the picture data of the start-frame stored in the internal memory in step S69 belongs for the argument N.
Further, the microprocessor Mp substitutes the value 0 for the argument R so as to decode the picture data sequentially from the picture data belonging to the GOP containing the start-frame.
Further, the microprocessor Mp quotes the address for searching the picture data belonging to the GOP wherein the picture data of the start-frame is contained based on the argument N+R, and it moves the optical pickup Pu to the record position of the picture data belonging to the GOP on the disc based on the address so that the microprocessor Mp searches and obtains the picture data belonging t the GOP wherein the picture data of the start-frame belongs.
After processing in step S77, it goes to the judging processing in step S78.
In step S78, it is discriminated whether or not the GOP wherein the picture data of the start-frame belongs, that is, the (N+R)-th GOP is a closed type.
Whether the (N+R)-th GOP is closed type or not is determined by the value 1 or 0 of the GOP type flag set in the internal memory of the microprocessor Mp in step S71 or S72.
It is discriminated that if the GOP type flag stored in the internal memory of the microprocessor Mp is “1” the GOP wherein the picture data of the start-frame belongs is a closed type, and if the GOP type flag is “0” the GOP is not a closed type.
Here, if the result of the determination of the GOP type is YES, that is, the microprocessor Mp determines the GOP as a closed type based on the GOP type flag, the process goes to step S79. However, if the result if NO, that is, the GOP is not a closed type, the process goes to step S80.
In step S79, the microprocessor Mp decodes the picture data of the (N+R)-th GOP, that is, the GOP containing the picture data of the start-frame by controlling the MPEG decoder Mpg. All of the decoded frame data are temporarily stored in the frame buffer Fb.
To start the reproduction of the picture data, the decoded picture data corresponding to the frames are forwarded to the video D/A converter Vda on the rear in the reproducing order from the B-picture data corresponding to the start-frame in the GOP.
In step S79, since the GOP wherein the picture data belongs is a closed type the B-picture data is able to be decoded by only the picture data belonging to the closed type GOP.
In step S80, the microprocessor Mp decodes the picture data of the (N+R)-th GOP, that is, the GOP containing the picture data of the S80 start-frame by controlling the MPEG decoder Mpg. All of the decoded frame data are temporarily stored in the frame buffer Fb.
Here, since the GOP containing the start-frame picture data is not a closed type, the B-picture data corresponding to the frame which is reproduced precede the frame of the I-picture is not able to be decoded.
Accordingly the frames corresponding to the B-pictures which are not decoded in this step S80 are not able to be forwarded to the video D/A converter.
Thus, in this step, the picture data of each frame corresponding to B-picture which is not decoded is excluded, and the picture data of the frame corresponding to the I-picture which is reproduced first in this GOP is forwarded to the video D/A converter Vda on the rear in the reproducing sequence.
In this time the picture of the frame corresponding to B-picture which was not decoded is not displayed on a screen of the monitor Mnt, while the reproduction starts at the picture of the frame corresponding to an I-picture. Then there occurs a problem which is so-called as “frame drop”.
The microprocessor Mp carries out the processes of steps S79 and S80, then it goes to the process of step S81.
In step S81, the picture data of the end-frame is fetched by the optical pickup Pu, and it is discriminated whether or not the reproduction of the end-frame is completed.
In case that the determination in step S81 results in “YES”, i.e., when it is determined that the reproduction of the picture of the end-frame is complete, the process of step S77 is again executed.
In this time, the microprocessor Mp again makes the optical pickup Pu move to search the picture data belonging to the N-th GOP containing the start-frame.
The picture data searched by the optical pickup are decoded in the MPEG decoder as mentioned above, and forwarded to the video D/A converter.
Steps from S77 to S81 form a conditional loop, wherein the picture data belonging to GOP is fetched by the optical pickup Pu sequentially, and it is decoded in the MPEG decoder Mpg, then it is reproduced in the monitor Mnt so as to reproduce the picture between the start-frame and the end-frame repetitively.
However, in case that the determination in step S81 results in “NO”, i.e., when it is not determined that the STOP-key has been pressed, and that the reproducing is not complete, the process goes to step S82.
In this time, the microprocessor Mp obtains the picture data up to the last frame in the (N+R)-th GOP which have been reproduced, and it decodes these data in the MPEG decoder Mpg.
Then, the microprocessor Mp temporarily stores these data in the frame buffer Fb, and after that the microprocessor Mp successively forwards the picture data of each frame to the video D/A converter Vda in the reproducing sequence until completing the reproduction of all of the frames in a GOP.
In step S83, the microprocessor Mp counts up the argument R for fetching the GOP, and stores the value R in the internal memory.
Next, the process goes to step S84.
In step S84, it is discriminated whether or not the repetitive reproduction is complete.
Specifically, the operation for determining whether or not the repetitive reproduction STOP-key which is provided on the key-input system Kb has been pressed is executed by the microprocessor Mp.
Here, when it is determined that the repetitive reproduction is not complete, the process goes to step S79.
In this time, in step S83, since the value R has been incremented by “1”, the reproduced picture data belongs to the following GOP.
That is, a series of steps S79 to S84 form a conditional loop for reproducing the picture data of each frame which belonging to the GOP under reproduction up to the end-frame.
The repetitive reproduction will be continued unless the microprocessor Mp determines the repetitive reproduction end-key mounted through a key-input system Kb has been pressed.
In step S84, when the microprocessor Mp determines that the repetitive reproduction is complete, the process returns to the main routine of FIG. 18 for the normal reproduction proceed from step S63 to step S66, via the node 3.
Here, the operation of the conventional coded picture data reproducing apparatus in case that the B-picture frame which is reproduced in preceding the I-picture in the GOP is designated as a start-frame (position A), then the end-frame (position B) is designated will be explained in reference to FIG. 21.
FIG. 21 illustrates the operation of the conventional coded picture data reproducing apparatus.
In FIG. 21, position A is a start-frame designated by the key input system Kb.
As shown in FIG. 21, position A as a start-frame, which picture data is corresponds to B-picture, is reproduced in preceding the frame corresponding to the I-picture.
Further in FIG. 21, position B is an end-frame designated by the key input system Kb.
The optical pickup Pu traces the truck to obtain the recorded picture data.
The MPEG decoder Mpg decodes the picture data and forwards the decoded picture data sequentially to the video D/A converter Vda. The video D/A converter Vda outputs the analog video signal corresponding to each frame, and the video signal is sequentially displayed on the monitor Mnt as a picture.
When the picture corresponding to the start-frame (position A) is displayed on the monitor Mnt, the key input system Kb specifies the start-frame.
Then, when the picture corresponding to the end-frame (position B) is displayed on the monitor Mnt, the key input system Kb specifies the end-frame. Thus the optical pickup Pu searches the GOP containing the start-frame.
In this time, the optical pickup Pu obtains the picture data belonging to the GOP which contains the picture data of the start-frame.
However, when the fetched GOP is not a closed type, the B-picture data that corresponds to the start-frame (position A) is not able to be decoded.
Accordingly, as illustrated by the broken-arrow line in FIG. 21, the frame at which the repetitive reproduction starts in following the reproduction of the end-frame will be a frame corresponding to the I-picture which preceeds two frames from the start-frame (position A). After that the repetitive reproduction is executed over the frame corresponding to the I-picture not but the start-frame (position A) and the end-frame (position B).
Here, the picture is displayed on the monitor Mnt in state of lacking two frames containing start-frame (position A), so the picture seems unnatural as a repetitive reproduction picture.
Further, there occurs the above-mentioned “frame drop”, and thus it is impossible to achieve a perfect repetitive reproduction .
As described above, in the standard coded picture data which is coded by using the predictive coding scheme of MPEG system, in GOP a bi-directional predictive coded picture (B-picture data) which is reproduced in preceding an intraframe coded picture (I-picture data) has to be decoded after fetching the picture data in GOP which is reproduced just before the B-picture data and decoding an interframe forward predictive coded picture data (P-picture data) corresponding to the frame reproduced last in the preceding GOP.
That is, in the conventional coded picture data reproducing apparatus, when the frame corresponding to a bi-directional predictive coded picture data is designated as a start-frame at repetitive reproduction, the repetitive reproduction is not carried out from the picture corresponding to the designated start-frame. Thus, it is not realized to perform the repetitive reproduction between the exact designated frames.
As mentioned above, the conventional coded picture data reproducing apparatus has a drawbacks that when a frame corresponding to the bi-directional predictive coded picture data is designated as a start-frame it is not able to reproduce the picture data corresponding to the designated start-frame at repetitive reproduction time.